PSA: your laptop, they know where it is.
Report excerpt:
'The conventional use of the inductive amplifier is to locate breaks in wires, even those buried in concrete. The typical wire detection range in a concrete wall is 10-20cm. '
Even if your laptop is turn off, there's one thing you can't stop that's still powering the device: The CMOS battery. It keeps the motherboard's clock running, supposedly the device can pick up the little ticks that it lets off. So it's better to take your device with you than leave it in the trunk.
And this has been today's public service announcement.